I suspect the OP is referring to the fact that Epic is also suing Google, because they consider the "inconveniences" that Google places on sideloading to be a form of unfair, illegal restriction. This strongly suggests that if Apple offered sideloading but still had the same fees and restrictions in the official App Store, Epic would still be suing them.
More importantly, Google does not prohibit sideloading. It simply does not make it convenient to do it.